IBM Personal Computer

The CGA video card, with a suitable modulator, could use an NTSC television set or an RGBi monitor for display; IBM's RGBi monitor was their display model 5153. The other option that was offered by IBM was an MDA and their monochrome display model 5151. It was possible to install both an MDA and a CGA card and use both monitors concurrently[121] if supported by the application program. For example, AutoCAD, Lotus 1-2-3 and others allowed use of a CGA Monitor for graphics and a separate monochrome monitor for text menus. Some model 5150 PCs with CGA monitors and a printer port also included the MDA adapter by default, because IBM provided the MDA port and printer port on the same adapter card; it was in fact an MDA/printer port combo card.

Although cassette tape was originally envisioned by IBM as a low-budget storage alternative, the most commonly used medium was the floppy disk. The 5150 was available with one or two ​5 1⁄4" floppy drives – with two drives the program disc(s) would be in drive A, while drive B would hold the disc(s) for working files; with one drive the user had to swap program and file discs into the single drive. For models without any drives or storage medium, IBM intended users to connect their own cassette recorder via the 5150's cassette socket. The cassette tape socket was physically the same DIN plug as the keyboard socket and next to it, but electrically completely different.

A hard disk could not be installed into the 5150's system unit without changing to a higher-rated power supply (although later drives with lower power consumption have been known to work with the standard 63.5 Watt unit). The "IBM 5161 Expansion Chassis" came with its own power supply and one 10 MB hard disk and allowed the installation of a second hard disk.[122] The system unit had five expansion slots, and the expansion unit had eight; however, one of the system unit's slots and one of the expansion unit's slots had to be occupied by the Extender Card and Receiver Card, respectively, which were needed to connect the expansion unit to the system unit and make the expansion unit's other slots available, for a total of 11 slots. A working configuration required that some of the slots be occupied by display, disk, and I/O adapters, as none of these were built into the 5150's motherboard; the only motherboard external connectors were the keyboard and cassette ports.

The simple PC speaker sound hardware was also on board.

The original PC's maximum memory using IBM parts was 256 kB, achievable through the installation of 64 kB on the motherboard and three 64 kB expansion cards. The processor was an Intel 8088 running at 4.77 MHz, 4/3 the standard NTSC color burst frequency of 315/88 = 3.57954[a] MHz. (In early units, the Intel 8088 used was a 1978 version, later were 1978/81/2 versions of the Intel chip; second-sourced AMDs were used after 1983)[citation needed]. Some owners replaced the 8088 with an NEC V20 for a slight increase in processing speed and support for real mode 80186 instructions. The V20 gained its speed increase through the use of a hardware multiplier which the 8088 lacked. An Intel 8087 coprocessor could also be added for hardware floating-point arithmetic.

IBM sold the first IBM PCs in configurations with 16 or 64 kB of RAM preinstalled using either nine or thirty-six 16-kilobit DRAM chips. (The ninth bit was used for parity checking of memory.) In November 1982, the ROM for the IBM PC was changed to allow the use of 64 Kbit chips (as opposed to the original 16 Kbit chips) -- the same RAM configuration as the soon-to-be-released IBM XT. (64 kB in one bank, expandable to 256kB by populating the other 3 banks.)

Although the TV-compatible video board, cassette port and Federal Communications Commission Class B certification were all aimed at making it a home computer,[46] the original PC proved too expensive for the home market. At introduction, a PC with 64 kB of RAM and a single 5.25-inch floppy drive and monitor sold for US $3,005 (equivalent to $8,281 in 2018), while the cheapest configuration (US $1,565) that had no floppy drives, only 16 kB RAM, and no monitor (again, under the expectation that users would connect their existing TV sets and cassette recorders) proved too unattractive and low-spec, even for its time (cf. footnotes to the above IBM PC range table).[123][124] While the 5150 did not become a top selling home computer, its floppy-based configuration became an unexpectedly large success with businesses.